One path to amassing a fortune is to identify the next big thing and invest in the companies poised to emerge as the leaders in it. For example, you might have bought shares of Microsoft in the early days of the PC or Amazon in the early innings of the internet.

What's the next big thing today? Quantum computing is a top candidate. But which quantum computing stocks are most likely to make you a millionaire?

High-risk, potentially high-reward

Let's start by looking at high-risk quantum computing stocks that could be massive winners over the long term. Some of them are already delivering jaw-dropping gains.

For example, Rigetti Computing's (RGTI 7.07%) share price has skyrocketed at least 1,000% over the last 12 months. Rigetti aims to be the leader in superconducting quantum computing. It has 17 quantum systems installed so far and recently introduced an 84-qubit quantum system called Ankaa-3.

Quantum Computing (QUBT 3.80%) is nipping at Rigetti's heels with a similar gain over the last 12 months. The aptly named company focuses on developing photonic integrated circuits for quantum computers. It has eight installations and is the only pure-play public company specializing in nonlinear quantum optics and integrated photonics.

D-Wave Quantum (QBTS 5.32%) is another quantum computing company receiving a lot of attention from investors. Its stock has jumped close to 590% over the last 12 months. D-Wave claims to have the world's largest quantum computer. The company has 132 customers, including 27 members of the Forbes Global 2000.

IonQ (IONQ 1.75%) already markets the Forte and Tempo quantum computers. The company has landed collaborations with major companies such as Ansys and AstraZeneca. It also won a $54.5 million contract to develop quantum systems for the U.S. Air Force Research Lab.

Arqit Quantum (ARQQ -4.52%) and Sealsq (LAES -0.94%) are two ancillary quantum computing stocks that have vaulted higher, albeit not at the level of the aforementioned stocks. Both companies provide solutions to protect technology from quantum computing threats. Arqit markets quantum-safe encryption software, while Sealsq makes quantum-resistant microcontrollers.

Established players

There are several alternatives in quantum computing for investors who prefer larger, established players. The biggest in this group is Microsoft. The tech giant's Azure Quantum is a cloud-based quantum computing service.

Google parent Alphabet (GOOG 1.47%) (GOOGL 1.57%) has arguably made the biggest splash in quantum computing over the last year. In December 2024, Google announced that its Willow quantum chip reduced errors exponentially as more qubits were used -- a major milestone for quantum computing.

IBM (IBM -1.00%) and Honeywell (HON -0.15%) have each been around for over 100 years. Both are also actively developing quantum computing technology. IBM claims to have "the largest quantum computing fleet in the world" with its Qiskit platform. Honeywell merged its quantum computing unit with Cambridge Quantum to form Quantinuum, which it bills as "the world's largest integrated quantum computing company." Although Quantinuum is privately held, Honeywell owns roughly 54% of the company.

Most likely millionaire makers

Theoretically, any of these quantum computing stocks could be millionaire makers with enough money invested up front and enough time. Smaller companies typically have more room to run. However, they also come with the most risk.

I think Rigetti deserves the spotlight it has received in recent months. I also view Quantum Computing, D-Wave, and IonQ as legitimate contenders in the quantum computing market. The problem is that it's impossible to know at this point which of these will ultimately be the most successful.

For aggressive investors willing to tolerate significant volatility and risk, perhaps the best strategy is to buy shares of each of them and wait. Keep in mind, though, that none of these stocks may deliver positive gains over the long term, much less be millionaire makers.

Among the established players, Alphabet appears to be the best bet to make $1 million over time. Sure, the company faces some risks -- notably including regulatory challenges. But I fully expect Alphabet's Google unit to continue dominating search for a long time to come.

I look for Google Cloud to keep growing rapidly. Waymo has a huge opportunity in the robotaxi market. And maybe, just maybe, Google will achieve its goal of building "a useful, error-corrected quantum computer" by the end of the decade.